An aerogel-based composite heat dissipation coating and a method of making the same

Abstract

This invention belongs to the field of aerogel materials technology in colloid chemistry, specifically relating to an aerogel-based composite heat dissipation coating and its preparation method. The preparation method includes the following steps: S1, preparing a silica sol using sodium metasilicate and hydrochloric acid as raw materials, and preparing an alumina sol using aluminum chloride hexahydrate, deionized water, and anhydrous ethanol as raw materials; then mixing the silica sol, the alumina sol, carbon nanocages, and propylene oxide, followed by supercritical drying to obtain a composite aerogel substrate; S2, preparing silver-containing graphene using graphene nanosheets and silver nitrate as raw materials, then combining it with carbon nanotubes to obtain a high thermal conductivity filler; mixing the high thermal conductivity filler with a binder to obtain a coating slurry; coating the coating slurry onto the surface of the composite aerogel substrate and subjecting it to heat treatment and vacuum drying to obtain the aerogel-based composite heat dissipation coating. This invention achieves both lightweight and high thermal conductivity while effectively increasing the mechanical properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of aerogel materials technology in colloid chemistry, specifically relating to an aerogel-based composite heat dissipation coating and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, the thermal management of battery packs has become increasingly prominent. Safety accidents caused by battery thermal runaway have become a major factor restricting the large-scale popularization of new energy vehicles. Lithium-ion batteries have high energy density, but during operation, the energy released by chemical reactions or the energy loss during charging generates a large amount of heat, causing the battery temperature to rise. If this heat cannot be dissipated in time, it will significantly affect the battery's performance and lifespan, and may lead to serious safety problems.

[0003] Battery thermal management technology plays a crucial role in ensuring efficient and stable battery operation, extending battery life, and preventing thermal runaway. Power batteries generate a significant amount of heat during charging and discharging, especially during high-rate charging and discharging, prolonged operation, or high-temperature environments. If heat cannot be dissipated or insulated effectively and promptly, the internal temperature of the battery will rise sharply, potentially leading to capacity degradation, performance decline, and even thermal runaway, severely impacting vehicle safety. Currently, common heat dissipation methods for battery packs include air cooling, liquid cooling, and heat sink attachment. However, existing heat dissipation materials often suffer from problems such as heavy weight, insufficient insulation, and uneven thermal conductivity. While aerogel materials possess excellent overall performance, their low thermal conductivity prevents direct application to areas requiring rapid heat dissipation.

[0004] Chinese patent (publication number CN118405942B) discloses a wide-temperature-range anti-oxidation coating for carbon aerogel composite materials and its room-temperature preparation method. This method involves uniformly coating a ceramic powder-resin slurry onto the surface of the carbon aerogel composite material and then drying it at room temperature. The resin's viscosity and cohesive force during drying cause the ceramic powder to form a tightly bound aggregate that adheres to the C / CA surface. During service, the synergistic effect of the ceramic phase's oxidative expansion self-sealing and the glass phase's flow self-healing achieves wide-temperature-range anti-oxidation. Compared to traditional coating preparation techniques, this room-temperature preparation method eliminates the need for high-temperature heat treatment, effectively preventing an increase in the thermal conductivity of the C / CA substrate. This patented technology is primarily used for wide-temperature-range anti-oxidation and cannot be used for heat conduction in battery pack casings; further improvements are needed in the material's compressive strength.

[0005] Therefore, there is an urgent need for an aerogel-based composite heat dissipation coating, which uses aerogel as a matrix and coats a slurry containing thermally conductive fillers to form a coating. This composite material has both lightweight and high-efficiency thermal conductivity, and its compressive strength is also improved, making it suitable for the field of heat dissipation in battery pack casings. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an aerogel-based composite heat dissipation coating and its preparation method. The invention first prepares a silica sol using sodium metasilicate and hydrochloric acid as raw materials, and an alumina sol using aluminum chloride hexahydrate, deionized water, and anhydrous ethanol as raw materials. Then, the silica sol, alumina sol, carbon nanocages, and propylene oxide are mixed to obtain a composite aerogel substrate. A high thermal conductivity filler and binder are then mixed to obtain a coating slurry, which is applied to the surface of the composite aerogel substrate. After heat treatment, the aerogel-based composite heat dissipation coating is obtained. Through the combined action of the aerogel substrate and the coating, both lightweight and high thermal conductivity are achieved, while effectively increasing the mechanical properties of the material, making it better suited for heat dissipation in battery pack casings.

[0007] In a first aspect, the present invention provides a method for preparing an aerogel-based composite heat dissipation coating, comprising the following steps:

[0008] S1. Silica sol is prepared using sodium metasilicate and hydrochloric acid as raw materials, and alumina sol is prepared using aluminum chloride hexahydrate, deionized water and anhydrous ethanol as raw materials. Then, the silica sol, the alumina sol, carbon nanocages and propylene oxide are mixed and subjected to supercritical drying to obtain a composite aerogel substrate.

[0009] S2. Silver-containing graphene is prepared using graphene nanosheets and silver nitrate as raw materials, and then composited with carbon nanotubes to obtain a high thermal conductivity filler. The high thermal conductivity filler and binder are mixed to obtain a coating slurry. The coating slurry is coated on the surface of the composite aerogel substrate and subjected to heat treatment and vacuum drying to obtain an aerogel-based composite heat dissipation coating.

[0010] As a preferred embodiment of the present invention, the preparation steps of the composite aerogel substrate in step S1 are as follows: by weight, 90-100 parts of a 1.5 mol / L sodium metasilicate aqueous solution and 90-100 parts of a 2 mol / L hydrochloric acid solution are mixed and stirred for 2-4 hours to obtain a silica sol; 20-24 parts of aluminum chloride hexahydrate, 18-22 parts of deionized water and 36-40 parts of anhydrous ethanol are mixed and stirred for 2-4 hours to obtain alumina sol; 180-200 parts of the alumina sol and 180-200 parts of the silica sol are mixed and 2-4 parts of carbon nanocages are added; the mixture is stirred at 50-60°C for 160-180 minutes to obtain a mixed sol; 50-60 parts of propylene oxide are added to the mixed sol and stirred in an ice bath for 4-6 hours; the mixture is allowed to stand for 60-80 minutes to obtain a mixed gel; the mixed gel is subjected to supercritical drying treatment to obtain the composite aerogel substrate.

[0011] As a preferred embodiment of the present invention, the sodium metasilicate aqueous solution may be in the following weight proportions: 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, or 100 parts.

[0012] As a preferred embodiment of the present invention, the weight parts of the aluminum chloride hexahydrate can be 20 parts, 21 parts, 22 parts, 23 parts, or 24 parts, etc.

[0013] As a preferred embodiment of the present invention, the alumina sol may be in the following weight proportions: 180 parts, 190 parts, or 200 parts, etc.

[0014] As a preferred embodiment of the present invention, the weight parts of the silica sol may be 180 parts, 190 parts, or 200 parts, etc.

[0015] As a preferred embodiment of the present invention, the carbon nanocage may be in the form of 2, 3, or 4 parts by weight.

[0016] As a preferred embodiment of the present invention, the weight parts of the propylene oxide may be 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, or 60 parts, etc.

[0017] As a preferred embodiment of the present invention, the conditions for the supercritical drying process are: drying temperature of 36~38℃, drying pressure of 7~8MPa, separation temperature of 42~44℃, and separation pressure of 5~6MPa.

[0018] As a preferred technical solution of the present invention, the preparation steps of the carbon nanocage are as follows: by weight, 4-6 parts of sucrose and 20-30 parts of potassium chloride are mixed and ground for 30-40 minutes, then transferred to a tube furnace for high-temperature carbonization treatment, and naturally cooled to room temperature to obtain carbon nanocage.

[0019] As a preferred embodiment of the present invention, the weight parts of the sucrose may be 4 parts, 5 parts, or 6 parts, etc.

[0020] As a preferred embodiment of the present invention, the potassium chloride may be present in weight parts of 20, 22, 24, 26, 28, or 30 parts, etc.

[0021] As a preferred technical solution of the present invention, the conditions for the high-temperature carbonization treatment are: heating at 5℃ / min to 780~800℃ and holding at that temperature for 120~140min.

[0022] This invention first mixes sodium metasilicate with hydrochloric acid, and generates silicic acid through an acid-base neutralization reaction, which then condenses to form silica. Next, using aluminum chloride hexahydrate as the aluminum source and ethanol and water as mixed solvents, the aluminum salt undergoes hydrolysis and condensation reactions in the water / alcohol solution to form alumina sol. Then, the two sols are mixed and carbon nanocages are added and stirred to disperse the mixture. Propylene oxide is used as a gelation promoter to control the pH of the system, promoting the formation of a uniform and continuous three-dimensional network structure. Finally, supercritical drying technology is used to gently remove the liquid solvent from the pores without damaging the three-dimensional network structure of the gel, thereby preparing a composite aerogel substrate.

[0023] As a preferred technical solution of the present invention, the preparation steps of the silver-containing graphene are as follows: by weight, 2-4 parts of graphene nanosheets are added to 300-400 parts of deionized water and ultrasonically dispersed for 60-80 min, then 10-20 parts of 0.1 mol / L silver nitrate solution are added and stirred for 50-60 min, then 10-20 parts of 0.2 mol / L sodium borohydride solution are added and stirred for 60-80 min, washed with deionized water, and dried to obtain silver-containing graphene.

[0024] As a preferred embodiment of the present invention, the graphene nanosheets may be in the following weight proportions: 2 parts, 3 parts, or 4 parts, etc.

[0025] As a preferred technical solution of the present invention, the preparation steps of the high thermal conductivity filler are as follows: by weight, 2-4 parts of silver-containing graphene and 0.2-0.4 parts of carbon nanotubes are added to 180-200 parts of N,N-dimethylformamide and ultrasonically dispersed for 20-30 min, electrostatically self-assembled at 40-50℃ for 2-4 h, filtered, washed with anhydrous ethanol, and freeze-dried to obtain the high thermal conductivity filler.

[0026] As a preferred embodiment of the present invention, the weight percentage of the silver-containing graphene may be 2 parts, 3 parts, or 4 parts, etc.

[0027] As a preferred embodiment of the present invention, the weight fraction of the aminated single-walled carbon nanotubes may be 0.2 parts, 0.3 parts, or 0.4 parts, etc.

[0028] As a preferred embodiment of the present invention, the carbon nanotubes are amination-modified single-walled carbon nanotubes.

[0029] As a preferred embodiment of the present invention, the binder is sulfonated polyvinyl alcohol; the preparation steps of the sulfonated polyvinyl alcohol are as follows: by weight, 20-30 parts of polyvinyl alcohol powder are added to 500-600 parts of deionized water, stirred and dissolved at 80-90°C, then transferred to an ice bath and 4-6 parts of concentrated sulfuric acid are added dropwise, and then placed in a water bath at 40-50°C and stirred for 4-6 hours, washed with anhydrous ethanol, and dried to obtain sulfonated polyvinyl alcohol.

[0030] As a preferred technical solution of the present invention, the preparation steps of the coating slurry are as follows: by weight, 6-8 parts of binder are added to 90-100 parts of dimethyl sulfoxide and stirred to dissolve, and then 2-4 parts of high thermal conductivity filler are added and stirred for 4-6 hours to obtain the coating slurry.

[0031] As a preferred embodiment of the present invention, the heat treatment conditions are: temperature of 130~140℃ and time of 6~8h.

[0032] This invention first disperses graphene nanosheets in water, then adds silver nitrate solution and sodium borohydride solution sequentially, and obtains silver-containing graphene through liquid-phase reduction. Then, the negatively charged silver-containing graphene is mixed with positively charged aminated carbon nanotubes in a solvent, and a high thermal conductivity filler is obtained through electrostatic attraction self-assembly. The high thermal conductivity filler is then mixed with sulfonated polyvinyl alcohol as a binder to form a slurry, which is then coated onto a composite aerogel substrate. After heat treatment, an aerogel-based composite heat dissipation coating is prepared.

[0033] A second aspect of the present invention provides an aerogel-based composite heat dissipation coating prepared by the preparation method described in the first aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) In this invention, silver-containing graphene and aminated single-walled carbon nanotubes are electrostatically self-assembled to form a high thermal conductivity filler, and sulfonated polyvinyl alcohol is used as a binder to prepare a coating slurry. Then, it is coated on a silica-alumina aerogel substrate containing carbon nanocages to form a heat dissipation coating. The sulfonic acid groups of sulfonated polyvinyl alcohol in the coating can form covalent bonds with the hydroxyl groups on the surface of the composite aerogel substrate. At the same time, the high thermal conductivity filler in the coating contains graphene and carbon nanotubes, which can be stacked π-π with the carbon nanocages in the aerogel, thereby improving the overall performance of the material by strengthening the interface.

[0036] (2) The carbon nanocages in the composite aerogel substrate of the present invention have hollow cavities and through-holes. The density is reduced by the hollow topology. Propylene oxide, as a gel promoter, controls the hydrolysis and condensation rate of silicon-aluminum species by slowly consuming protons, avoiding the formation of dense agglomerates by local rapid precipitation, thereby further reducing the apparent density of the composite material. On the other hand, the carbon nanocages are uniformly dispersed and embedded in the inorganic network to play a bridging role, which can effectively prevent crack propagation and improve mechanical properties. The carbon nanocages can also form a synergistic effect with the silica-alumina aerogel skeleton. Combined with the slow gelation controlled by propylene oxide, the internal stress concentration points are reduced, thereby significantly improving the compressive strength of the material.

[0037] (3) In the high thermal conductivity filler of the present invention, aminated carbon nanotubes and silver-containing graphene are tightly bonded together by electrostatic attraction to form a three-dimensional interconnected hybrid filler. The long and curved carbon nanotubes can inhibit the aggregation of graphene and also increase the mutual contact between fillers to build a more efficient heat transfer network, which significantly improves the thermal conductivity of the material. The three-dimensional network structure formed by the self-assembly of the filler in the coating is itself a high porosity skeleton. When it is dispersed in sulfonated polyvinyl alcohol, it can build a large-volume heat conduction path with less solid mass, thereby effectively reducing the material density. Graphene nanosheets provide large-area planar support to hinder crack propagation. Carbon nanotubes are connected between graphene sheets as nanopillars. Nano silver particles can prevent irreversible slippage and stacking of graphene sheets under pressure. The three-dimensional interlocking network formed by electrostatic self-assembly has extremely high modulus and can significantly enhance the mechanical properties of the material. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0039] Figure 1 The infrared spectra of the composite aerogel substrate and silica aerogel in Example 1 of the present invention are shown.

[0040] Figure 2 The Raman spectra of the high thermal conductivity filler and graphene nanosheets in Example 1 of this invention are shown. Detailed Implementation

[0041] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0042] The sources of some components in the examples and comparative examples are as follows:

[0043] Sodium metasilicate, CAS No. 6834-92-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0044] Aluminum chloride hexahydrate, CAS No. 7784-13-6, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0045] Propylene oxide, CAS No. 75-56-9, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] Sucrose, CAS No. 57-50-1, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0047] Potassium chloride, CAS No. 7447-40-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0048] Graphene nanosheets, item number 102179, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0049] Silver nitrate, CAS No. 7761-88-8, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0050] Sodium borohydride, CAS No. 16940-66-2, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0051] Aminated single-walled carbon nanotubes, item number C140994, were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0052] Commercially available single-walled carbon nanotubes, item number C434641, were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0053] Commercially available polyvinyl alcohol powder, product number P434372, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Example 1:

[0055] This embodiment provides a method for preparing an aerogel-based composite heat dissipation coating, including the following steps:

[0056] S1. By weight, 100 parts of a 1.5 mol / L sodium metasilicate aqueous solution and 100 parts of a 2 mol / L hydrochloric acid solution were mixed and stirred for 4 h to obtain a silica sol. 24 parts of aluminum chloride hexahydrate, 22 parts of deionized water and 40 parts of anhydrous ethanol were mixed and stirred for 4 h to obtain alumina sol. 200 parts of the alumina sol and 200 parts of the silica sol were mixed and 4 parts of carbon nanocages were added. The mixture was stirred at 60 °C for 180 min to obtain a mixed sol. 60 parts of propylene oxide were added to the mixed sol and stirred in an ice bath for 6 h. After standing for 80 min, a mixed gel was obtained. The mixed gel was subjected to supercritical drying treatment (drying temperature 38 °C, drying pressure 8 MPa, separation temperature 44 °C, separation pressure 6 MPa) to obtain a composite aerogel substrate.

[0057] S2. By weight, 4 parts of graphene nanosheets were added to 400 parts of deionized water and ultrasonically dispersed for 80 min. Then, 20 parts of 0.1 mol / L silver nitrate solution were added and stirred for 60 min. Next, 20 parts of 0.2 mol / L sodium borohydride solution were added and stirred for 80 min. The mixture was washed with deionized water and dried to obtain silver-containing graphene. 4 parts of silver-containing graphene and 0.4 parts of aminated single-walled carbon nanotubes were added to 200 parts of N,N-dimethylformamide and ultrasonically dispersed for 30 min. Electrostatic self-assembly was carried out at 50℃ for 2 h. The mixture was filtered, washed with anhydrous ethanol, and freeze-dried to obtain a high thermal conductivity filler. 8 parts of sulfonated polyvinyl alcohol as a binder were added to 100 parts of dimethyl sulfoxide and stirred to dissolve. Then, 4 parts of the high thermal conductivity filler were added and stirred for 6 h to obtain a coating slurry. The coating slurry was coated on the surface of a composite aerogel substrate and heat-treated (temperature 140℃, time 6 h). The substrate was then vacuum dried to obtain an aerogel-based composite heat dissipation coating.

[0058] Preparation of the carbon nanocage: By weight, 6 parts of sucrose and 30 parts of potassium chloride were mixed and ground for 40 min, and then transferred to a tube furnace for high-temperature carbonization treatment. The temperature was increased to 800℃ at 5℃ / min and held for 120 min. The mixture was then naturally cooled to room temperature to obtain the carbon nanocage.

[0059] Preparation of the sulfonated polyvinyl alcohol: 30 parts by weight of polyvinyl alcohol powder are added to 600 parts of deionized water and stirred and dissolved at 90°C. Then, 6 parts of concentrated sulfuric acid are added dropwise under ice bath conditions, and the mixture is stirred in a water bath at 50°C for 4 hours. After washing with anhydrous ethanol and drying, sulfonated polyvinyl alcohol is obtained.

[0060] Figure 1 The infrared spectra of the composite aerogel substrate and silica aerogel are shown, with the 879 cm⁻¹ spectrum being the most significant. -1 The left and right sides represent the absorption peaks of the stretching vibrations of the Al-O-Al bond, at 1024 cm⁻¹. -1 The left and right sides are absorption peaks for the stretching vibrations of the Si-O-Si bond, at 3386 cm⁻¹. -1 The left and right sides represent the absorption peaks of the stretching vibration of OH. Figure 2 Raman spectra of high thermal conductivity fillers and graphene nanosheets, with the 1350 cm⁻¹ peak value being the highest. -1 1580cm -1 and 2708cm -1 The peaks at this position are characteristic peaks of graphene nanosheets. Since the high thermal conductivity filler is prepared based on graphene nanosheets, the position of the characteristic peaks is not significantly changed, but the intensity of these peaks is enhanced.

[0061] Example 2

[0062] This embodiment provides a method for preparing an aerogel-based composite heat dissipation coating, including the following steps:

[0063] S1. By weight, 90 parts of a 1.5 mol / L sodium metasilicate aqueous solution and 90 parts of a 2 mol / L hydrochloric acid solution were mixed and stirred for 2 hours to obtain a silica sol. 20 parts of aluminum chloride hexahydrate, 18 parts of deionized water and 36 parts of anhydrous ethanol were mixed and stirred for 2 hours to obtain alumina sol. 180 parts of the alumina sol and 180 parts of the silica sol were mixed and 2 parts of carbon nanocages were added. The mixture was stirred at 50°C for 180 minutes to obtain a mixed sol. 50 parts of propylene oxide were added to the mixed sol and stirred in an ice bath for 4 hours. After standing for 60 minutes, a mixed gel was obtained. The mixed gel was subjected to supercritical drying treatment (drying temperature 36°C, drying pressure 7 MPa, separation temperature 42°C, separation pressure 5 MPa) to obtain a composite aerogel substrate.

[0064] S2. By weight, 2 parts of graphene nanosheets were added to 300 parts of deionized water and ultrasonically dispersed for 60 min. Then, 10 parts of 0.1 mol / L silver nitrate solution were added and stirred for 50 min. Next, 10 parts of 0.2 mol / L sodium borohydride solution were added and stirred for 60 min. The mixture was washed with deionized water and dried to obtain silver-containing graphene. 2 parts of silver-containing graphene and 0.2 parts of aminated single-walled carbon nanotubes were added to 180 parts of N,N-dimethylformamide and ultrasonically dispersed for 20 min. Electrostatic self-assembly was carried out at 40℃ for 4 h. The mixture was filtered, washed with anhydrous ethanol, and freeze-dried to obtain a high thermal conductivity filler. 6 parts of sulfonated polyvinyl alcohol as a binder were added to 90 parts of dimethyl sulfoxide and stirred to dissolve. Then, 2 parts of the high thermal conductivity filler were added and stirred for 4 h to obtain a coating slurry. The coating slurry was coated on the surface of a composite aerogel substrate and heat-treated (temperature 130℃, time 8 h). The substrate was then vacuum-dried to obtain an aerogel-based composite heat dissipation coating.

[0065] Preparation of the carbon nanocage: By weight, 4 parts of sucrose and 20 parts of potassium chloride were mixed and ground for 30 min, and then transferred to a tube furnace for high-temperature carbonization treatment. The temperature was increased to 780℃ at 5℃ / min and held for 140 min. The mixture was then naturally cooled to room temperature to obtain the carbon nanocage.

[0066] Preparation of the sulfonated polyvinyl alcohol: 20 parts by weight of polyvinyl alcohol powder are added to 500 parts of deionized water and stirred and dissolved at 80°C. Then, 4 parts of concentrated sulfuric acid are added dropwise under ice bath conditions, and the mixture is stirred in a water bath at 40°C for 6 hours. After washing with anhydrous ethanol and drying, sulfonated polyvinyl alcohol is obtained.

[0067] Example 3

[0068] This embodiment provides a method for preparing an aerogel-based composite heat dissipation coating, including the following steps:

[0069] S1. By weight, 95 parts of a 1.5 mol / L sodium metasilicate aqueous solution and 95 parts of a 2 mol / L hydrochloric acid solution were mixed and stirred for 3 h to obtain a silica sol. 22 parts of aluminum chloride hexahydrate, 20 parts of deionized water and 38 parts of anhydrous ethanol were mixed and stirred for 3 h to obtain alumina sol. 190 parts of the alumina sol and 190 parts of the silica sol were mixed and 3 parts of carbon nanocages were added. The mixture was stirred at 55 °C for 170 min to obtain a mixed sol. 55 parts of propylene oxide were added to the mixed sol and stirred in an ice bath for 5 h. After standing for 70 min, a mixed gel was obtained. The mixed gel was subjected to supercritical drying treatment (drying temperature 37 °C, drying pressure 7.5 MPa, separation temperature 43 °C, separation pressure 5.5 MPa) to obtain a composite aerogel substrate.

[0070] S2. By weight, 3 parts of graphene nanosheets were added to 350 parts of deionized water and ultrasonically dispersed for 70 min. Then, 15 parts of 0.1 mol / L silver nitrate solution were added and stirred for 55 min. Next, 15 parts of 0.2 mol / L sodium borohydride solution were added and stirred for 70 min. The mixture was washed with deionized water and dried to obtain silver-containing graphene. 3 parts of silver-containing graphene and 0.3 parts of aminated single-walled carbon nanotubes were added to 190 parts of N,N-dimethylformamide and ultrasonically dispersed for 25 min. Electrostatic self-assembly was carried out at 45℃ for 3 h. The mixture was filtered, washed with anhydrous ethanol, and freeze-dried to obtain a high thermal conductivity filler. 7 parts of sulfonated polyvinyl alcohol as a binder were added to 95 parts of dimethyl sulfoxide and stirred to dissolve. Then, 3 parts of the high thermal conductivity filler were added and stirred for 5 h to obtain a coating slurry. The coating slurry was coated on the surface of a composite aerogel substrate and heat-treated (temperature 135℃, time 7 h). The substrate was then vacuum-dried to obtain an aerogel-based composite heat dissipation coating.

[0071] Preparation of the carbon nanocage: By weight, 5 parts of sucrose and 25 parts of potassium chloride were mixed and ground for 35 min, and then transferred to a tube furnace for high-temperature carbonization treatment. The temperature was increased to 790℃ at 5℃ / min and held for 130 min. The mixture was then naturally cooled to room temperature to obtain the carbon nanocage.

[0072] Preparation of the sulfonated polyvinyl alcohol: 25 parts by weight of polyvinyl alcohol powder were added to 550 parts of deionized water and stirred and dissolved at 85°C. Then, 5 parts of concentrated sulfuric acid were added dropwise under ice bath conditions, and the mixture was stirred in a water bath at 45°C for 5 hours. The mixture was then washed with anhydrous ethanol and dried to obtain sulfonated polyvinyl alcohol.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is that no carbon nanocages are added during the preparation of the composite aerogel substrate.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 1 is that commercially available ordinary single-walled carbon nanotubes (product number C434641) were used instead of aminated single-walled carbon nanotubes in the preparation of the high thermal conductivity filler.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 1 is that commercially available polyvinyl alcohol powder (product number P434372) was used instead of sulfonated polyvinyl alcohol in the preparation of the coating slurry.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 1 is that no high thermal conductivity filler is added during the preparation of the coating slurry.

[0081] The performance of the above embodiments and comparative examples was tested using the following methods:

[0082] (1) Apparent density test: Under the conditions of temperature of 25℃ and humidity of 45%, the mass m of the sample is accurately weighed, and the volume V of the sample is measured by the water displacement method, and the apparent density is calculated.

[0083] (2) Thermal conductivity test: The test shall be conducted in accordance with the requirements of ISO 22007-2:2022.

[0084] (3) Compression strength test: The compression performance of the examples and comparative examples was tested using an electronic universal testing machine (Instron 5982, USA). The sample size was 10mm×10mm×10mm, and the maximum stress at 10% strain was used to characterize the compression strength.

[0085] The performance test data above are shown in Table 1.

[0086] Table 1 Performance Test Results

[0087] ;

[0088] As can be seen from the above, the present invention first prepares silica sol using sodium metasilicate and hydrochloric acid as raw materials, and prepares alumina sol using aluminum chloride hexahydrate, deionized water and anhydrous ethanol as raw materials. Then, silica sol, alumina sol, carbon nanocages and propylene oxide are mixed to prepare a composite aerogel substrate. Then, a high thermal conductivity filler and binder are mixed to obtain a coating slurry and coated on the surface of the composite aerogel substrate. After heat treatment, an aerogel-based composite heat dissipation coating (Examples 1 to 3) is obtained, which has the best comprehensive performance.

[0089] Compared to Example 1, no carbon nanocages were added during the preparation of the composite aerogel substrate. The lack of carbon nanocages resulted in a decrease in apparent density and compressive strength (Comparative Example 1). Compared to Example 1, commercially available ordinary single-walled carbon nanotubes (item number C434641) were used instead of aminated single-walled carbon nanotubes during the preparation of the high thermal conductivity filler. The lack of aminated single-walled carbon nanotubes resulted in a decrease in apparent density, compressive strength, and thermal conductivity (Comparative Example 2). Compared to Example 1, commercially available polyvinyl alcohol powder (item number P434372) was used instead of sulfonated polyvinyl alcohol during the preparation of the coating slurry. The lack of sulfonated polyvinyl alcohol resulted in a decrease in compressive strength (Comparative Example 3). Compared to Example 1, no high thermal conductivity filler was added during the preparation of the coating slurry. The lack of high thermal conductivity filler resulted in a decrease in apparent density, compressive strength, and thermal conductivity (Comparative Example 4).

Claims

1. A method for preparing an aerogel-based composite heat dissipation coating, characterized in that, Includes the following steps: S1. A silica sol is prepared using sodium metasilicate and hydrochloric acid as raw materials, and an alumina sol is prepared using aluminum chloride hexahydrate, deionized water, and anhydrous ethanol as raw materials. The silica sol, the alumina sol, carbon nanocages, and propylene oxide are then mixed and subjected to supercritical drying to obtain a composite aerogel substrate. S2. Silver-containing graphene is prepared using graphene nanosheets and silver nitrate as raw materials. It is then composited with aminated single-walled carbon nanotubes to obtain a high thermal conductivity filler. The high thermal conductivity filler and a binder are mixed to obtain a coating slurry. The coating slurry is coated on the surface of the composite aerogel substrate and subjected to heat treatment and vacuum drying to obtain an aerogel-based composite heat dissipation coating. The preparation steps of the high thermal conductivity filler are as follows: by weight, 2-4 parts of silver-containing graphene and 0.2-0.4 parts of aminated single-walled carbon nanotubes are added to 180-200 parts of N,N-dimethylformamide and ultrasonically dispersed for 20-30 min. Electrostatic self-assembly is carried out at 40-50℃ for 2-4 h. After filtration, washing with anhydrous ethanol, and freeze-drying, the high thermal conductivity filler is obtained.

2. The method for preparing an aerogel-based composite heat dissipation coating according to claim 1, characterized in that, The preparation steps of the composite aerogel substrate in step S1 are as follows: by weight, 90-100 parts of 1.5 mol / L sodium metasilicate aqueous solution and 90-100 parts of 2 mol / L hydrochloric acid solution are mixed and stirred for 2-4 hours to obtain silica sol; 20-24 parts of aluminum chloride hexahydrate, 18-22 parts of deionized water and 36-40 parts of anhydrous ethanol are mixed and stirred for 2-4 hours to obtain alumina sol; 180-200 parts of the alumina sol and 180-200 parts of silica sol are mixed and 2-4 parts of carbon nanocages are added, and the mixture is stirred at 50-60℃ for 160-180 minutes to obtain a mixed sol; 50-60 parts of propylene oxide are added to the mixed sol and stirred in an ice bath for 4-6 hours; the mixture is allowed to stand for 60-80 minutes to obtain a mixed gel; and the mixed gel is subjected to supercritical drying treatment to obtain the composite aerogel substrate.

3. The method for preparing an aerogel-based composite heat dissipation coating according to claim 2, characterized in that, The conditions for the supercritical drying process are as follows: drying temperature of 36~38℃, drying pressure of 7~8MPa, separation temperature of 42~44℃, and separation pressure of 5~6MPa.

4. The method for preparing an aerogel-based composite heat dissipation coating according to claim 2, characterized in that, The preparation steps of the carbon nanocage are as follows: by weight, 4-6 parts of sucrose and 20-30 parts of potassium chloride are mixed and ground for 30-40 minutes, then transferred to a tube furnace for high-temperature carbonization treatment, and naturally cooled to room temperature to obtain carbon nanocage.

5. The method for preparing an aerogel-based composite heat dissipation coating according to claim 1, characterized in that, The preparation steps of the silver-containing graphene are as follows: by weight, 2-4 parts of graphene nanosheets are added to 300-400 parts of deionized water and ultrasonically dispersed for 60-80 min, then 10-20 parts of 0.1 mol / L silver nitrate solution are added and stirred for 50-60 min, then 10-20 parts of 0.2 mol / L sodium borohydride solution are added and stirred for 60-80 min, washed with deionized water, and dried to obtain silver-containing graphene.

6. The method for preparing an aerogel-based composite heat dissipation coating according to claim 1, characterized in that, The binder is sulfonated polyvinyl alcohol; the preparation steps of the sulfonated polyvinyl alcohol are as follows: by weight, 20-30 parts of polyvinyl alcohol powder are added to 500-600 parts of deionized water, stirred and dissolved at 80-90°C, then transferred to an ice bath and 4-6 parts of concentrated sulfuric acid are added dropwise, and then placed in a water bath at 40-50°C and stirred for 4-6 hours, washed with anhydrous ethanol, and dried to obtain sulfonated polyvinyl alcohol.

7. The method for preparing an aerogel-based composite heat dissipation coating according to claim 1, characterized in that, The preparation steps of the coating slurry are as follows: by weight, 6-8 parts of binder are added to 90-100 parts of dimethyl sulfoxide and stirred to dissolve, and then 2-4 parts of high thermal conductivity filler are added and stirred for 4-6 hours to obtain the coating slurry.

8. An aerogel-based composite heat dissipation coating, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

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